Electric cable



July 9, 1946, J, URMSTQN 2,403,693

- ELECTRIC CABLE Filed Dc. l2, 1941 E E m ATTORNEY ag.

resented July e, 194s ELECTRIC CABLE James Urmston, Montclair, N. J., 4assigner to C allenders Cable Construction, Co., Ltd.,-

London, England Appuentien neeemhell 12, 1941, serial No. 422,650

7 Claims. 1

Ifhis invention relates to an improvement in electric cables, and has for one-of its objects the provision of a cable which is capable of carrying relatively large currents but which at the same time is suillclently buoyant to float in water,

The usual electric cable combining conductor and insulation has a density 'much greater than guished from a material such as so-called sponge rlgber in whichtl'e'cells communicate with each o H" i I A 1- I. .i' 1. y

There are several methods of making the core. One method is to incorporate i'nto an unvulcanized rubber compound a gas-producing material, that is, a*materlalwhich decomposes and gives oftgas when heated', vso :that when the rubber compound is being vulcanized by heat the gas thereby f ormed will expand the rubber into a body having myria'ds of :non-intercommunicating cells. The walls of the cells are very thin and exceedingly so in the' caseci highly gassed material, so that diffusion of gas from or bursting More specifically the present invention provides an electric cable in which the conductor is built up about a core of highly buoyant material, the conductor in turn being properly insulated with waterex`cludinginsulating material.

Still more specifically the present invention provides a cable such as'above briefly outlined in which the core referred vto is of cellular material, that-is, a material composed of myriads of gasfilled non-communicating cells, the conductor being stranded'cir-braided, preferably the former, about this core.l Thecore-may be continuous or it may be in relatively short lengths. When rela# tively short lengths are employed then partitions or discs of wood, for example, are provided between adjacent lengths, which function to act as y from the core, but for easecf manufacture the integral construction is preferred.

Reverting to the material of the core: The core has been referred to as constructed of "cellular" material,v and as above pointed out this term -is to `bel interpreted to Acover a material composed of gas-lilled-"non-communicating cells, as :listinfof the cells on the outside surface can be expected, causing -progres'sive'deiiationof the cells from outside to inside the nialteriad-` Aside iromthe-fact that the cable core is cellular, 'it is'to be noted'that the core may be made from various materials.' By way of example, materials such as natural rubber, artificial rubber and thermoplastics may be mentioned, and any of these can be made cellular by vvadding gas-producing' compounds and then heating.4

As to the skin or sheath or covering in which the 'core is enclosed: As above pointed out the cells oi vthe core vare thin-walled, and a certain amountv of gas" diffusion-and cell bursting is to be expected, with a consequent decrease'in the overall dimensions of the core. It is tov prevent'this loss of gas and consequent decrease in the core that I provide the skin, sheath or covering. There are many Ways in which this element can be producedf In the case of a continuous core. the core may be drawn through a latex bath and then vulcanized; or a layer of rubber may be lapped around the core' material. In the case of short lengths the' cprecompound can be enclosed in u'nvul'canized rubber. In all cases the skin can be applied to the corelmateriai before the latter has-been'heated, so that upon `heating the core material can be formed into la; cellular mass and the core and skin vulcanized'simultaneously.

The external dimensions of the finished product would be determined by the size and shape of the mould or container in which the vulcanization takes place.

As above pointed out the skin or sheath functions to-.support the walls of the cells on the surface ofthe core andprevent excessive gas diffu'- sion and bursting of the cells; the skin, however, which is relatively gas impervious, serving to retain any-gas which mightescape from the cells.

In the accompanying drawing several embodiments of the cable have been illustrated.`

bodiment of my invention;

Fig. 1 is a fragmentary longitudinal section of a cable constructed in accordance with one emr'ig. 2 is a section on the une z -z of rig. r1;

Fig. 3 is a view similar to Fig. 1 of another embodiment of the invention;

Fig. 4 is a view similar to Fig. 1 of still another embodiment of the invention; and

Figs. 5 and 6 are cross sectional views of two other embodiments of the invention.

Referring to the drawing in detail as shown in Figs. 1 and 2, the cable includes a buoyant core 4 of cellular material provided with a gas impermeable skin or sheath 8. A conductor 8 is built up about the core and is conveniently made-of copper strands braided Ior stranded about the core. Insulation l which surrounds the conductor may be rubber or any other suitable water resistant material.

Thegcore 4 in this embodiment of the invention is continuous throughout the length of the cable. The gas impervious skin or sheath 6 also extends continuously the length of the core. and about the ends of the core as well. As above pointed out the core is of lcellular material, that is to say, it is composed of myx-lads of gas-filled thin-walled non-intercommunicating cells. It is evident that this skin or sheath supports the walls oi.' the cells on the surface of the cellular core, and prevents excessive diffusion of gas through the cell walls, while any gas that might escape is retained by the skin. This construction prevents detrimental loss of gas from the core I and consequent shrinkage of the core, so that the danger of sufiicient water entering the cable between the core and conductor to sink the cable is avoided.

In the embodiment of the invention illustrated in Fig. 3, the core, which is of the same material as the core 4 already referred to, instead of extending continuously throughout the cable as in Figs. 1 and 2, is made in relatively short lengths designated I2. These relatively short lengths are spaced from each other by a partition or dise i4 preferably of wood. These wooden discs act as a support for the cable conductor to prevent pulling down of the same when the cable is subjected to a longitudinal stress.

In this embodiment of the invention each core length I2 is completely enclosed in a relatively gas impermeable skin or sheath 6 which is the same as the skin or sheath 6 of Figs. l and 2.

The embodiment of the invention illustrated;

in Fig. 4 is identical with that of Fig. 3 except that instead of providing a gas impermeable skin or sheath 8 for each individual core length, the skin or sheath is continuous and completely encloses the core lengths and thediscs i4.

In the embodiment of the invention illustrated in Fig. I provide a. buoyant cable comprising relatively short lengths of cellular material, these lengths being designated i6. They are similar to the lengths I2 of FigB/Y in that each is completely enclosed in a gas impermeable skin or sheath IB. These core lengths, in practice, will be separated from each other vby conductor-supporting wooden discs similar to the discs i4 of Figs. 3 and 4. Surrounding the core assembly is a rubber tube 20. Gas under pressure is introduced between the skin I8 and this tube, sumcient pressure being employed to cause the tube to contact the conductor 8 throughout the length of the cable, and also to compress the core lengths, which, so long as they contain their original gas charge and are not placed under compression are of such dimensions as to illl the tube 2li to hold it against the conductor. In the event that this cable is punctured, allowing the gas t0 escape from the space between the core and tube, it will be apparent that the lengths I8 will expand thereby illling the tube 2li and forcing it against the conductor to prevent the ingress o! sunlcient water to sink the cable.

The construction in Fig. 6 is similar to that of Fig. 5, except that the skin I8 of Fig. 5 has been omitted. When using this type of construction I prefer to use the same kind of gas between the core I6 and the tube 20 as is employed in the cells of the core, to reduce diffusion of gas from the core.

In both Figs. 5 and 6 I may employ continuous cores as distinguished from relatively short lengths, if desired.

For purposes of clarity I have made no attempt in any of the drawings to show the 'cells of the core material. l

A5 above pointed out the core may be made from various materialsnot necessarily of rubber-but in all cases must be composed of myriads of gas-filled'non-communicating cells. The mode of making the core material does not constitute part of this invention, inasmuch as the core material may be made by processes existing prior to this invention.

The skin or sheath of Figs. 1 to 5 is essential, and as described may be continuous throughout the length of the cable or discontinuous j it may be separate lfrom or integral with the core material; but in all cases it must be relatively gas impermeable, suiciently so in any event to prevent any substantial loss of gas out `of the core.

It is to be uderstood that various changes may be made in the details of construction and arrangement of parts hereinabove shown and described wlthout departing from the spirit and scope of the invention.

I claim:

l. An electric cable comprising a central flexible core of cellular material composed of gasnlled, non-intercommunicating cells, a relatively gas-impermeable skin or sheath around the longitudinal surface of the core, an annular flexible conductor about the skin or sheath, and an insulating and Water-excluding covering surrounding the conductor, the whole assembly `'providing a flexible cable which will float on water.

2. An electric cable comprising a continuous ilexible core of cellular material enclosed in a relatively gas-impermeable covering, an annular ilexible conductor built up about the core, and an insulating water-excluding covering surrounding the conductor, the assembly providing a flex- 4ible cable capable of iloating in Water..

lengths of cellular material, each length being completely surrounded with a relatively gas-impermeable covering.

5. A buoyant electric cable comprising an annular ilexible conductor, a core substantially filling the space within the conductor, said core including relatively short lengths oflcellular material composed of gas-illled, non-intercommuand water-excluding non-metallic sheath surrounding the conductor. 4

7. A buoyant electric cable comprising a central core comprising relatively short lengths ot a material composed of non-intercommunicating gas-filled cells. each length being completely surrounded by a relatively gas-impermeable skin or sheath, wooden discs intermediate adjacent core lengths, an annular flexible conductor about the core, and an insulating and water-excluding non-- metallic sheath surrounding the conductor.

JAMES URMs'roN. 

